Forced vibration piezo generator and piezo actuator

ABSTRACT

Piezoelectric elements for power generation and/or actuation are described. An aspect is directed to generators utilizing piezoelectric elements for electrical power generation. Such a generator can use one or more arrays of piezoelectric cantilevers for electrical power generation in conjunction with modulated air pressure used for exciting the cantilevers. The pressure level/modulation and cantilever area can be controlled variables for maximizing the bending, and hence energy generation, of the cantilevers. A further aspect is directed to hydraulic fluid actuators utilizing a pumping mechanism that includes a piezoelectric element. The linear actuators can advantageously utilize the high force and high frequency characteristics of a piezoelectric membrane in conjunction with a large stroke and actuation direction conversion afforded by hydraulic transmission.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.12/334,383, filed Dec. 12, 2008, which claims priority from U.S.Provisional Patent Application No. 61/007,497, filed Dec. 12, 2007, bothof which are incorporated herein by reference in their entireties.

BACKGROUND

Power generating devices that harvest energy from natural environmentsare widely researched and devices that provide “free” energy are alwaysdesired. The concept and technology for generating electrical power fromvibrating piezoelectric (“piezo”) cantilever beams is known and is inuse for power harvesting in vibrating environments. In these devices, anarray of piezo cantilever beams is fabricated on a substrate, usuallyusing thin film micro-electromechanical systems (“MEMS”) processes, anda small proof mass is deposited or otherwise attached to the free end ofeach beam. As the device holding the substrate vibrates, the cantileversstart vibrating at their natural frequency (resonate) with the proofmass being the element that induces the bending force on the beam. Thepiezo cantilever beams are constructed in a way that when they bend, anelectrical voltage is generated between the top and bottom surfaces, andwhen connected to an electrical circuit, electrical current develops.Such devices use vibration from the environment as their energy sourceand the magnitude of the cantilevers' bending and electrical energyproduced is limited by the energy in this vibration and the geometry ofthe beams, mainly their cross section and weight of proof mass. Since inmost cases of energy harvesting from vibration, the available energy isnot very high and since the proof mass (comparing to the stiffness ofthe beams) is not large, the bending of the piezo beams is small and theamount of energy produced is also not high.

Power generation using compressed air is also a known technique. Typicalair pressure power generators use the air's kinetic energy as a means torotate some kind of turbine that in turn rotates an electromagneticgenerator. This kind of air pressure generators require high pressurelevels and are relatively big and heavy. They also have inherent startuplosses due to the need to accelerate the moving masses before power isgenerated.

In the area of actuating devices, or actuators, for some MEMS basedapplications such as fluidic microchannel chip cooling devices, ahigh-force, large-stroke high-frequency actuator is required. Currentactuators in the MEMS world do not meet these three high performancerequirements. As a result the desired performance of the device cannotbe met.

There are several MEMS based linear actuator technologies. The mostcommon one is the electrostatic comb-drive actuator that deliverslarge-stroke actuation at high frequencies but with limited force andwith limitations on its size that reduce scalability potential to largerforce actuators. On the other side of the spectrum is the thermalactuator that delivers large stroke and high force at a very lowfrequency. Other actuation technologies include stacked piezo layers(high force and frequency and very small stroke. Not really a MEMSactuator), Piezo membrane (high force and small stroke) and others. Noneof the existing known actuators deliver the combination of these threeperformance characteristics.

While the prior art techniques may prove suitable for certain intendeduses, for other applications such techniques can be subject tolimitations.

SUMMARY

The present disclosure is directed to techniques, including devices,apparatus, methods, and systems that address deficiencies note for theprior art. Aspects/embodiments of the present disclosure can utilizepiezoelectric elements for power generation and/or displacement orposition control (actuation).

An aspect of the present disclosure is directed to generators utilizingpiezoelectric elements for electrical power generation. Such generatorscan utilize one or more arrays of piezoelectric cantilevers inconjunction with modulated fluid pressure used for exciting thecantilevers for electrical power generation. The pressurelevel/modulation and cantilever area can be controlled variables,allowing for maximizing the bending, and hence energy generation, of thecantilevers. In exemplary embodiments, the pressure modulation frequencyis designed to match the designed resonance frequency of the beams inorder to achieve best/optimal energy conversion efficiency.

An exemplary embodiment of a piezoelectric generator according to thepresent disclosure can include a generator plate comprising a pluralityof piezoelectric cantilevers. The generator can also include an inletand valving plate including an inlet for receiving fluid and an aperturefor passing fluid to the generator plate. An exhaust plate can bepresent that includes an exhaust aperture configured and arranged toreceive fluid from the generator plate. The generator plate can includea piezoelectric membrane configured and arranged to receive anelectrical signal and in response modulate pressure of a fluid providedfrom the aperture to the plurality of piezoelectric cantilevers.

A further embodiment can include a system of stacked piezoelectricgenerator modules and a throttle piston configured and arranged forbeing disposed within the inlet of each generator module to be throttledfor selectively opening or blocking the flow groove of the individualgenerator modules.

A further aspect of the present disclosure is directed to hydraulic(fluid) actuators utilizing a pumping mechanism that includes apiezoelectric element. The linear actuators can advantageously utilizethe high force and high frequency characteristics of a piezoelectricmembrane in conjunction with a large stroke and actuation directionconversion afforded by hydraulic transmission.

An exemplary embodiment of a piezohydraulic linear actuator inaccordance with the present disclosure can include (i) a housingincluding a fluid reservoir, (ii) a piezoelectric element actuatorincluding a moveable membrane supported on a surface adjacent the fluidreservoir and a piezoelectric element supported by the membrane, whereinthe piezoelectric element is configured and arranged to undergodeformation out of the plane of the membrane in response to an appliedelectric field, and (iii) a movable surface coupled to the fluidreservoir.

Other features and advantages of the present disclosure will beunderstood upon reading and understanding the detailed description ofexemplary embodiments, described herein, in conjunction with referenceto the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure may be more fully understood from thefollowing description when read together with the accompanying drawings,which are to be regarded as illustrative in nature, and not as limiting.The drawings are not necessarily to scale, emphasis instead placed onthe principles of the disclosure. In the drawings:

FIG. 1 depicts a diagrammatic perspective view of a forced vibrationpiezoelectric generator (“FVPG”) module in accordance with an exemplaryembodiment of the present disclosure;

FIG. 2 depicts the generator module of FIG. 1 with transparent inlet andvalving plate;

FIG. 3 shows a cross section of the generator module of FIGS. 1-2;

FIG. 4 depicts a diagrammatic cross section of a seven layer FVPG stack,in accordance with an exemplary embodiment of the present disclosure;

FIG. 5 depicts a diagrammatic perspective view of a piezohydraulicactuator with a moving shuttle and viscous material seal, in accordancewith a further embodiment of the present disclosure;

FIG. 6 depicts a schematic view of a cross section of a piezohydraulicactuator showing mounting of the piezoelectric element and its mode ofdeflection, in accordance with exemplary embodiments of the presentdisclosure;

FIG. 7 depicts a diagrammatic perspective view of a shuttle layer for apiezohydraulic actuator, in accordance with an embodiment of the presentdisclosure;

FIG. 8 depicts a diagrammatic perspective view with cross section of apiezohydraulic actuator with a bellows wall design, in accordance withexemplary embodiments of the present disclosure;

FIG. 9 depicts a diagrammatic perspective view of a piezohydraulicactuator with a moving shuttle and viscous material seal, in accordancewith a further embodiment of the present disclosure;

FIG. 10 depicts a diagrammatic perspective view of an integratedactuator micro pump design, in accordance with a further embodiment ofthe present disclosure; and

FIG. 11 depicts a scanning electron micrograph of an embodiment of apiezohydraulic actuator, in accordance with an exemplary embodiment ofthe present disclosure.

While certain embodiments depicted in the drawings, one skilled in theart will appreciate that the embodiments depicted are illustrative andthat variations of those shown, as well as other embodiments describedherein, may be envisioned and practiced within the scope of the presentdisclosure.

DETAILED DESCRIPTION

The present disclosure is, in general terms, directed to techniques,including devices, apparatus, systems, and methods for power generationand/or displacement control (actuation) for small scale (e.g., MEMS)devices and systems. Exemplary embodiments can utilize piezoelectricelements.

Forced Vibration Piezo Generators

An aspect of the present disclosure is directed to generators utilizingpiezoelectric elements/materials for electrical power generation. Such agenerator can use one or more arrays of piezoelectric cantilevers forelectrical power generation in conjunction with modulated fluid pressureused for exciting the cantilevers. As used herein, “fluid” can includereference to a liquid or a gas, though exemplary embodiments aredescribed in the context of the fluid being air. Embodiments ofharvesting devices of the present disclosure that use low pressure, lowkinetic energy pressurized air can potentially replace large andexpensive wind turbines that only work at strong winds areas and areaimed only at the high power applications.

Such generators can utilize one or more arrays of piezoelectriccantilevers, or “piezo cantilever arrays,” for electrical powergeneration. Instead of using a proof mass and excitation by externalvibration (as in prior art vibration energy harvesting devices), suchgenerators can use forced and/or modulated air pressure as the means forexciting the cantilevers. In exemplary embodiments, a piezoelectricmembrane can be controlled to modulate the pressure of air (or otherfluid) sent to the piezo cantilever arrays. The pressure level andcantilever area can be controlled variables for maximizing the bending,and hence energy generation, of the cantilevers. Accordingly, suchgenerators are sometimes referred to herein as forced vibrationpiezoelectric generators (“FVPGs”), In exemplary embodiments, thepressure modulation frequency provided, e.g., by a piezo membrane, isdesigned to match the designed resonance frequency of the cantileverbeams in order to achieve best energy conversion efficiency.

Such FVPG systems can be considered pure pressure systems as theyutilize the pressure differential between pulsating air and the ambientair pressure to bend the cantilever beams. Because of this reason, theFVPG system can produce energy even at low air pressure levels and lowflow rate. The flow rate is proportional to the number of beams operated(which can be controlled as will be explained below) and the resonancefrequency designed into the beams. Because pressure uses the area of thebeam for creating a bending force, the actual bending forces on acantilever beam from a relatively low pressure are much larger than anyvibration induced forces with typical proof mass and environmentvibration levels. Also, a vibration energy harvesting device onlycaptures the vibration energy at a frequency that coincides with thepiezo cantilevers' resonance frequency. The remaining vibration energyis lost.

Pressurized air can come from different sources including manual pumps(e.g., a small manual pump to pressurize a small air tank), an intakemanifold in a moving vehicle (an unmanned aerial vehicle “UAV” that usesan engine for flying but needs an electrical power source for poweringits payload) or wind (similar to the UAV application where the intakemanifold is placed in a windy environment). Although in all of theseexamples the kinetic energy may not be very high, a pressuredifferential is created that can be used in FVPGs according to thepresent disclosure.

In exemplary embodiments of the present disclosure, a FVPG preferably(though not necessarily) modulates air pressure to the resonancefrequency of the cantilever beams so most of the energy stored in theair pressure will be used to excite the beams. An exemplary embodimentdescribed below presents a FVPG configuration that allows control of theamount of electrical energy generated with different levels of airpressure and flow by providing a stacked configuration of FVPGs inconjunction with a throttle bore.

FIG. 1 depicts a diagrammatic perspective view of the basic buildingblock of a FVPG generator module 100 in accordance with exemplaryembodiments of the present disclosure. Module 100 consists of threeplates bonded/configured adjacent to one another: an air inlet andvalving plate 110, a generator plate 120, and an exhaust plate 130.

With continued reference to FIG. 1, close to the edge of the module 100there is an aperture or inlet hole 112 that is used as the air inletpath to the module 100. In exemplary embodiments, inlet 112 can passthrough the generator plate 120 and exhaust plate 130, as will bedescribed. As shown, the air inlet and valving plate 110 can include asmall hole 114 in the center and a groove 116 on its top side thatconnects this hole 114 to the inlet hole 112. The generator plate 120can include one or more (preferably many) piezo cantilevers, e.g.,configured concentric arrays residing around a central piezo membrane(as shown in FIG. 2). The exhaust plate 130 includes ports or exhaustpassages that allow air to pass from the generator plate 120 to outsidethe module 100.

In exemplary embodiments, the generator plate 120 can be made fromsilicon and the piezo cantilevers and central piezo membrane can befabricated using a thin-film fabrication processes, e.g., sputtering orsol gel processes. Suitable piezo materials for the cantilevers and/ormembrane can include, but are not limited to, zinc oxide, bariumtitanite, lead titanite, lead zirconate titanate, lead lanthanumzirconate titanate, lead magnesium niobate, potassium niobate, potassiumsodium niobate, and/or potassium tantalite niobate, among others.Piezoelectric polymers may be used in exemplary embodiments of thepresent disclosure.

FIG. 2 depicts the piezo generator module 100 of FIG. 1 with transparentinlet and valving plate 110. As previously described, the generatorplate 120 can include a plurality of piezo cantilevers 122. Thecantilevers 122 are preferably configured as concentric circular arrays.The generator plate 120 can include a central membrane 124 that isconfigured to act as a modulating valve for air coming through thecentral hole 114 in the inlet and valving plate 110. In alternateembodiments, the central membrane 124 can be connected to or integralwith the inlet and valving plate 110. Suitable electrical connections orelectrodes are included (not shown) for causing actuation/movement ofthe central membrane 124 and also to receive electrical power generatedfrom the cantilevers 122 as they move; such electricalconnections/electrodes may be separate for each different function.

With continued reference to FIG. 2, as the valve membrane 122 isactuated up and down, it moves towards and away from the valve hole 114,opening and closing it thus modulating the air flow. Pressurized airpulses move into the volume above the cantilever beams 122 and applybending forces or loading profiles on them. As the beams 122 bend theycreate an electrical response due to their piezoelectric nature. Also,as the beams bend, the air passes through the small gaps 126 that openbetween the beams 122 and the plate 120 (shown in FIG. 3) and enters anexhaust port or volume 132. This volume 132 can be a gap created by theexhaust plate 130. The air passes through the exhaust volume 132 to bereleased outside of the module, e.g., into a manifold or the ambientair.

FIG. 3 shows a cross section of the generator module 100 of FIGS. 1-2.The beams 122 and membrane 124 are shown as a thin layer on the top sideof the generator plate 120. When bonded together, the membrane 124 makescontact with the valve hole (zero gap) but it is free to move back,e.g., in response to an applied voltage. As the membrane 124 moves, agap opens to allow air to flow in a radial direction to the volumeabove/surrounding the piezo cantilever beams 122. As the beams 122 bend,the air passes through the small gaps 126 that open between the beams122 and the plate 120, producing electrical energy that can beharvested, e.g., through appropriate electrical connections. The fluid(e.g., air or other gas) then enters an exhaust port or volume 132 inthe exhaust plate 130.

When the membrane 124 moves towards the hole 114, the membrane 124presses against the hole 114 and completely shuts the flow of air intothe generator plate 120. Since the diameter of the membrane 124 can bemuch larger than the diameter of the valve hole 114, and since theblocking force of a piezo element can be relatively high, the valvingforce of the membrane 124 can be higher than the force generated by thepressurized air even at high pressure levels. The FVPG 100 can bedesigned in this way with the-expected pressure of the specificapplication in mind.

The pressure at different concentric beam arrays drops for furtherarrays due to the release of air in previous concentric arrays. This candictate the number of concentric arrays that can generate power in onegenerator module. Depending on the performance goals and available airpressure, the number of concentric arrays can vary from one to several.

One skilled in the art will understand that while an exemplaryembodiment of implementing a FVPG is described with regard to FIGS. 1-3,other embodiments and implementation methods are within the scope of thepresent disclosure and can also utilize the basic concept of forcedvibration of piezo cantilever beams through modulation of air pressure.

FIG. 4 depicts a cross section of a system 400 of stacked FVPGs inaccordance with an exemplary embodiment of the present disclosure. Asshown, system 400 can include multiple FVPG modules 402 stackedtogether, e.g., the seven FVPGs 402(1)-402(7). A throttle piston 404 isconfigured and arranged to move up and down in an air pressure inlethole 406 that is shared by the stacked FVPGs 402(1)-402(7). By such aconfiguration, the throttle piston 404 can be throttled to selectivelyopen or block the flow grooves in the individual modules 402(1)-402(7)in a sequential manner. The piston 404 can move from a closed position(no power generated, no air consumed) to a full open position, andthrough a range of positions in between the two extremes. In exemplaryembodiments, the actuation of the respective membrane valves can also becontrolled by the relative position of the throttle piston 404 so thatno membrane will be actuated when no air is supplied to thecorresponding module 402.

With continued reference to FIG. 4, in exemplary embodiments, the piston404 can be automatically controlled (by available pressure for example)to adjust the electrical power generation (and air consumption) to theamount of available air. The piston 404 can also (or in the alternative)be controlled in an open (or closed) control loop (manually orotherwise) to increase or decrease the electrical power generation incases where enough air pressure is available.

In an exemplary embodiment, two loaded cantilever beam cases wereanalyzed using the Comsol MultiPhysics simulation program. A 50 μm thickpiezo beam (PZT-5H), 1 mm wide and 2.5 mm long was loaded with twodifferent loads. The first case illustrates a vibration energyharvesting piezo beam typical of the prior art. A 0.5 mm long×0.1 mmwide×0.5 mm thick proof mass was mounted at the end of the beam in thesimulation and a 1 g acceleration load was applied. The proof mass wasmodeled as being made from the same material and its mass was 1.875 e-6Kg. The end force for 1 g was 18.375 e-6N. The maximum deflection forthis case was shown to be 4.5 e-8 m or 0.045 μm.

The second case illustrates the simulation results of a pressure of 0.05atm applied to the top surface of the beam in accordance with anembodiment of the present disclosure. The maximum deflection for thisload was shown to be 1.1 e-5 m or 11 μm, which displacement is betweentwo and three orders of magnitude (244×) than the displacementcalculated for the case for the simulated proof mass.

Both loads illustrated for the above-described simulations wererelatively small loads. A load resulting from 1 g can be obtained fromrelatively mild vibration environments and pressure buildup of 0.05 atmis easily obtained using manual pump or designing a Pitot typecompressor in a moving vehicle. Still in these two mild load cases thepressure based case produced approximately 250 times larger deflection.As the voltage generated by a piezo cantilever beam is proportional tothe deflection and for a fixed geometry, the larger the deflection thehigher the voltage and total power. Accordingly, FVPGs systems/modulesof the present disclosure can offer advantages over prior art powergenerators.

Linear Actuators

A further aspect of the present disclosure is directed to hydraulic(fluid) linear actuators utilizing a pumping mechanism that includes apiezoelectric, electromagnetic, or electrostatic actuating element.Exemplary embodiments of the linear actuators can advantageously utilizethe high force and high frequency characteristics of a piezoelectricmembrane in conjunction with a large stroke and actuation directionconversion afforded by hydraulic transmission. Such actuators can fitinto MEMS devices that require high-force large-stroke actuation both inlow and more uniquely high frequency applications.

FIG. 5 depicts a diagrammatic perspective view of a piezohydrauliclinear actuator 500, in accordance with a further embodiment of thepresent disclosure. As shown in FIG. 5, the piezohydraulic actuator 500can include a housing and a piezoelectric actuator element 504. Theactuator 500 also includes a moving surface, e.g., shuttle 506. Aviscous material seal (not shown) can be included within the actuator500. The piezoelectric element actuator 504 component can includes asubstrate, e.g., silicon or metallic, on which a piezo material disk iseither deposited or otherwise attached. Housing 502 can include holes orapertures, e.g., holes 508 for hydraulic fluid filling and/or holes 509for viscous fluid filling. In exemplary embodiments piezoelectricelement 504 can be configured as a disk. Of course, while actuatorelement 504 is described as being a piezoelectric element actuator, inalternative embodiments, it may be or include a suitable electromagneticor electrostatic actuating element.

The mode of operation for the piezoelectric element actuator 504 isbending in and out of the static plane of the element 504 (disk). Forsuch operation, an included piezo disk (shown as the top surface 504 inFIG. 5) expands and contracts in the radial direction when subjected toa voltage difference in the thickness direction, e.g., as applied bysuitable electrodes/electrical connections. As a result of thisexpansion and contraction a non-symmetrical force is applied on thesubstrate material and bending occurs. The force in the directionperpendicular to the disk plane (blocking force) of such devices isrelatively high. For example, a disk that consists of a piezo crystallayer laminated on a brass substrate can produce more than 2 Newtons offorce with the center deflection proportional to the disk diameter. Thepiezo membrane/disk can be fabricated using a thin-film fabricationprocesses, e.g., sputtering or sol gel processes. Suitable piezomaterials for the membrane/disk can include, but are not limited to,zinc oxide, barium titanite, lead titanite, lead zirconate titanate,lead lanthanum zirconate titanate, lead magnesium niobate, potassiumniobate, potassium sodium niobate, and/or potassium tantalite niobate,among others. Piezoelectric polymers may be used in exemplaryembodiments of the present disclosure.

As previously described, the piezo disk actuator 504 can be mounted onhousing 502, which can be constructed in a way that all its side walls,e.g., wall 510 and the wall opposite to the piezo disk are rigid and onewall is flexible or includes a movable surface, e.g., fluidicallycoupled to shuttle 506 by way of a viscous fluid, to produce controlledlinear actuation. The flexible design can be achieved in a number ofways including a bellows wall, a piston-like slide with sealing meansand a shuttle on flexures, again with sealing means. FIG. 5 shows ashuttle 506 configured as a piston-like slide while FIG. 8 shows abellows wall embodiment.

Stroke enhancement for the actuator 500 can be achieved by designing theratio between the disk area and piston (or shuttle or bellows wall) areain a way that the small disk deflection displaces a volume of hydraulicfluid that produces a large piston movement. The actuation directionconversion is achieved by making the flexible wall one of the side wallsof the housing 502. For alternate embodiments, if no directionconversion is needed, the wall in front of the disk can be the actuationwall with a different pressure area (most of the wall rigid with a smallflexible part or a piston in it.

The design of the piezohydraulic actuator 500 allows for great designflexibility capable of producing a large set of force/strokecombinations. The design parameters include the disk size and originalforce and stroke parameters and the piston pressure area. In addition,the design of the actuator 500 is easily scalable to larger strokes andforces for various embodiments, for example as shown and described forFIGS. 6-11 herein.

FIG. 6 depicts a schematic view of a cross section of a portion of piezoactuator 600, in accordance with exemplary embodiments of the presentdisclosure. As shown in FIG. 6, actuator 600 can include a housing 601and a substrate 602 supporting a piezo disk 604. The mode of deflectionof the coupled substrate 602 and piezo disk 604 are indicated by thepositions 602A, 604A and 602B, 604B, respectively. When the disk 604vibrates in response to an applied voltage (field), displaced hydraulicfluid 606 can be utilized for linear actuation, e.g., fluid movingthrough channel 608 can push and pull a connected shuttle or bellows.

FIG. 7 depicts a perspective view of a shuttle layer 700 for a piezoactuator in accordance with an embodiment of the present disclosure. Asuitable actuator includes the shuttle layer 700 with housing 702 andmovable shuttle 704, and additional top and bottom layers (not shown)that constitute the hydraulic chamber and piezo disk membrane support. Apiezo disk, e.g., disk 604 of FIG. 6, would be attached to a membranesupport on the top layer to form an operational piezohydraulic actuatoraccording to the present disclosure.

Continuing with the description of FIG. 7, shuttle 704 has a “H” shape.One side/surface of shuttle 704 and the housing 702 form a hydraulicchamber suitable for holding hydraulic fluid, e.g., operated on by apiezo disk/membrane. Another side/surface of shuttle 704 can form or belinked to an actuation surface.

In exemplary embodiments, layer 700 can include flexures 708, e.g.,serpentine elements as shown, so as to provide/facilitate a springfunctionality to shuttle 704. Also, layer 700 can include a viscousfluid within chambers 710 for similar purposes.

FIG. 8 depicts a perspective view with cross section of a piezohydraulicactuator 800 with a bellows wall design, in accordance with exemplaryembodiments of the present disclosure. Actuator 800 is similar topiezohydraulic actuator 500 if FIG. 5, and includes a housing 802 onwhich is mounted a piezo actuator disk 804. The housing forms areservoir 808 for holding a hydraulic fluid and includes a moveablesurface 806. Instead of a shuttle or piston, however, actuator 800includes a bellows portion 810.

FIG. 9 depicts a perspective view of a piezohydraulic actuator 900 witha moving shuttle and viscous material seal, with lid and piezo diskremoved, in accordance with a further embodiment of the presentdisclosure. Actuator 900 includes a housing 902 a shuttle 904 that hastwo piston portions A and B. Housing 902 can be configured as shown toprovide a hydraulic chamber 906 and a sealing chamber 908 suitable forholding a viscous material, e.g., fluid. Actuator 900 can also includeflexures 910 (shown simplified in FIG. 9), similar to those of FIG. 7.

While the previous description of the embodiments of FIGS. 5-9 have beendirected to embodiments of stand-alone piezohydraulic linear actuators,piezohydraulic actuator according to the present disclosure can ofcourse be integrated into a final device being actuated by applying thehydraulic pressure waves directly on the end-actuated feature. This mayproduce simpler system designs and a reduction in the overall mass ofmoving parts which will improve the dynamic performance and allow higheroperation frequencies.

FIG. 10 depicts a perspective view of an integrated actuator micropump1000, in accordance with a further embodiment of the present disclosure.As shown, micropump 1000 can include a multiple housings 1001 formingpressure chambers 1002. Each pressure chamber 1002 can receive ahydraulic fluid. The fluid can be subject to pressure control by a piezodisk actuator (not shown), e.g., similar to those shown for FIGS. 5-6.Each pressure chamber 1002 can accordingly control a corresponding pumprib 1004. The movement of the ribs 1004 so produced can be utilized,e.g., for fluid pumping/cooling. The pump 1000 can also include housingportions 1010 and 1012 and flexures 1008 as shown.

FIG. 11 depicts a scanning electron micrograph of an embodiment of apiezohydraulic actuator shuttle layer 1100, in accordance with anexemplary embodiment of the present disclosure. The actuator can includea shuttle/piston 1102 suitable for moving fluid in a reservoir,represented by area 1104. The actuator shuttle layer includes a housing1106 and flexures 1108. The layer shown was formed by a deep reactiveion etch (“DRIE”) process on a 500μ thick silicon wafer.

Testing design embodiments of piezohydraulic actuators according to thepresent disclosure include a bulk piezo disk from Piezo Systems Inc.(T216-A4N0-273X having 2.4 N blocking force and 19μ. zero-load centerdeflection) mounted on a stainless steel foil over a sealed hydraulicchamber. Calculated operation parameters for the embodiment are 200μ p-pstroke and 76 E-3N force.

While certain embodiments have been described herein, it will beunderstood by one skilled in the art that the methods and treatments ofthe present disclosure may be embodied in other specific forms withoutdeparting from the spirit thereof. For example, while embodiments ofFVPGs have been described in the context of using air as an input fluid,the use of other gases or suitable liquids are within the scope of thepresent disclosure. For further example, while generators of the presentdisclosure have been described in the context of including an internalpiezo membrane for pressure modulation, external pressure modulation maybe utilized according to embodiments of the present disclosure.Additionally, while linear actuators have been described herein in thecontext of including a piezo membrane for causing hydraulic actuation(pressure modulation of a hydraulic fluid), in alternative embodiments,suitable electromagnetic or electrostatic actuating elements/actuatorscan be utilized.

Accordingly, the embodiments described herein, and as claimed in theattached claims, are to be considered in all respects as illustrative ofthe present disclosure and not restrictive.

1. An actuator comprising: a housing including a fluid reservoir; apiezoelectric actuator adjacent the fluid reservoir, wherein thepiezoelectric actuator includes a piezoelectric element configured todeform in response to an applied electric field to displace fluid in thefluid reservoir; and a movable surface hydraulically coupled to thefluid reservoir and configured for movement in response to displacementof the fluid in the fluid reservoir.
 2. The actuator of claim 1, whereinthe piezoelectric actuator comprises at least one material selected fromthe group consisting of zinc oxide, barium titanite, lead zirconatetitanate, lead lanthanum zirconate titanate, lead magnesium niobate,potassium niobate, potassium sodium niobate, potassium tantaliteniobate, and piezoelectric polymers.
 3. The actuator of claim 1, whereinthe fluid reservoir contains a hydraulic fluid.
 4. The actuator of claim1, wherein the movable surface is coupled to the housing by a bellows.5. The actuator of claim 1, wherein the movable surface is coupled tothe housing by a flexure.
 6. The actuator of claim 1, wherein themovable surface comprises a piston.
 7. The actuator of claim 1, whereinthe movable surface is separated from the housing by a seal configuredto constrain the fluid in the fluid reservoir.
 8. The actuator of claim1, wherein the housing and the movable surface aremicroelectromechanical systems.
 9. A system comprising: a plurality ofpump chambers, wherein each of the plurality of pump chambers includes ahousing comprising a fluid reservoir, and a pump rib hydraulicallycoupled to the fluid reservoir; and a piezoelectric actuatorhydraulically coupled to the fluid reservoir; wherein the pump rib isconfigured to pump a fluid.
 10. The system of claim 9, wherein thepiezoelectric actuator comprises at least one material selected from thegroup consisting of zinc oxide, barium titanite, lead zirconatetitanate, lead lanthanum zirconate titanate, lead magnesium niobate,potassium niobate, potassium sodium niobate, potassium tantaliteniobate, and piezoelectric polymers.
 11. The system of claim 9, whereinthe fluid reservoir contains a hydraulic fluid.
 12. The system of claim9, wherein each pump rib is coupled to the housing of the respectivepump chamber by a flexure.
 13. The system of claim 9, wherein each pumprib comprises a piston.
 14. A method comprising: applying a voltageacross a piezoelectric element of a piezoelectric actuator, wherein theapplied voltage causes the piezoelectric element to deform such that afluid in a fluid reservoir is displaced; wherein displacement of thefluid causes movement of a movable surface hydraulically coupled to thepiezoelectric element.
 15. The method of claim 14, further comprisingmodifying the voltage applied across the piezoelectric element tocontrol movement of the movable surface.
 16. The method of claim 14,wherein the piezoelectric actuator comprises at least one materialselected from the group consisting of zinc oxide, barium titanite, leadzirconate titanate, lead lanthanum zirconate titanate, lead magnesiumniobate, potassium niobate, potassium sodium niobate, potassiumtantalite niobate, and piezoelectric polymers.
 17. The method of claim14, wherein the movable surface is connected to the housing by abellows, the method further comprising passing fluid toward the movablesurface through the bellows.
 18. The method of claim 14, wherein themovable surface is connected to the housing by a flexure.
 19. The methodof claim 14, wherein the movable surface comprises a piston.
 20. Themethod of claim 14, wherein the movable surface is separated from thehousing by a seal configured to constrain a fluid in the fluidreservoir.
 21. A method comprising: applying a voltage across apiezoelectric element of a piezoelectric actuator, wherein the appliedvoltage causes deformation of the piezoelectric element such that afluid in a fluid reservoir of a pump chamber is displaced; wherein thedisplacement of the fluid causes a change in pressure in the pumpchamber and movement of a pump rib associated with the pump chamber. 22.The method of claim 21, further comprising pumping a second fluid inaccordance with movement of the pump chamber.
 23. The method of claim21, wherein the piezoelectric actuator comprises at least one materialselected from the group consisting of zinc oxide, barium titanite, leadzirconate titanate, lead lanthanum zirconate titanate, lead magnesiumniobate, potassium niobate, potassium sodium niobate, potassiumtantalite niobate, and piezoelectric polymers.
 24. The method of claim21, wherein the fluid reservoir contains a hydraulic fluid.
 25. Themethod of claim 21, wherein each pump rib is connected to the housing ofthe respective pump chamber by a flexure.
 26. The method of claim 21,wherein each pump rib comprises a piston.